Parking brake systems are used to create a parking brake force to prevent movement of a stopped or parked vehicle. In disc brake systems, the parking brake system moves a pair of opposing brake pads into engagement with a brake rotor to create the parking brake force. In drum-in-hat brake systems, the parking brake system moves a pair of brake shoes radially outward against the drum portion of a brake rotor to create the parking brake force.
In some applications, parking brake systems are electromechanical systems that include a motor and an actuator assembly for moving the brake pads or the brake shoes against the brake rotor, or the drum portion of a brake rotor, respectively, to create the parking brake force. Some known parking brake systems use a position sensor to determine a position of the actuator assembly and/or a position of one or more brake pistons to determine that the parking brake force has been created or released.
However, to reduce cost, space, and weight, and to comply with updated vehicle guidelines and recommendations, it may be desirable to have a parking brake system that does not include such a position sensor. That is, instead of a position sensor, it may be desirable to have control logic capable of accurately estimating and determining the position of the actuator assembly, a brake piston, a motor, or a combination thereof in order to determine that the parking brake force has been created or released. It may be attractive to have an accurate system or model for relating translational displacement of an actuator assembly and/or brake piston to a parking brake force.
Some examples of controlling a parking brake system are disclosed in U.S. Patent Application Numbers US 2013/338895 and US 2013/338896, and in U.S. Pat. Nos. 8,794,720 B2 and 8,825,326 B2, all of which are expressly incorporated by reference herein for all purposes.